Semiconductor component and method for producing the same

ABSTRACT

A method for producing a semiconductor component has the following step: the front side ( 101 ) of the semiconductor body ( 100 ) is irradiated with high-energy particles using the terminal electrode ( 40 ) as a mask, in order to produce recombination centers ( 80 A,  80 B) in the semiconductor body ( 100 ) for the recombination of the first and second conduction type of charge carriers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 11/246,345 filed Oct. 7, 2005 now U.S. Pat. No. 7,319,250,which is a continuation of co-pending International Application No.PCT/EP2004/003321 filed Mar. 29, 2004, which designates the UnitedStates of America, and claims priority to German application number DE103 16 222.4 filed Apr. 9, 2003, the contents of which are herebyincorporated by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a method for producing a verticalsemiconductor component which has a semiconductor body having an innerregion, at least one pn junction in the inner region and an edge regionthat is arranged between the inner region and an edge. A current flowsthrough components of this type when a suitable voltage is applied inthe vertical direction, that is to say perpendicular to a front and aback of the semiconductor body. U.S. Pat. No. 6,351,024 B1, for example,describes a vertical semiconductor component of this type having aninner region, which has a pn junction, and an edge region that adjoinsthe inner region.

BACKGROUND

When switching off semiconductor components of this type, that is to saywhen applying a voltage at which the pn junction is reverse-biased, theedge region is particularly important, as explained briefly below. Inthe case of a forward-biased pn junction, the edge regions are likewiseflooded with charge carriers, that is to say electrodes and holes, as aresult of diffusion. When switching off the component, these chargecarriers need to be removed from the edge regions, which results in theneed to dissipate a considerably higher charge in those regions of theinner region which adjoin the edge region than in the other regions ofthe inner region. The charge carriers, particularly holes, which flowout of the edge regions during the switching-off operation may, in thiscase, contribute to the production of additional charge carriers(avalanche effect), which leads to increased switching losses as aresult of the avalanche effects which begin dynamically and, in theworst case, to destruction of the component. This current density whichis higher in the edge region than in the inner region during theswitching-off operation limits the currents which can be switchedoverall using the component.

In order to alleviate this problem, it is known, in principle, from theabovementioned U.S. Pat. No. 6,351,024 B1, to shorten the charge carrierlifetime in the edge region. This is effected, for example, by producingadditional recombination centers by irradiating the edge region withhigh-energy particles. The disadvantage of the known method is that acomplicated technique using metallic masks which are difficult to adjustis required. In addition, it is also advantageously intended to shortenthe charge carrier lifetime in the inner region of the component, whichrequires a second complicated mask and irradiation technique.

SUMMARY

Therefore, it is an object of the present invention to provide a simpleand cost-effective method for producing a vertical semiconductorcomponent having improved switch-off properties and to provide avertical semiconductor component having improved switch-off properties.

This object can be achieved by a method for producing a semiconductorcomponent, said method comprising the following method steps ofproviding a semiconductor body which has a front side, a back side, aninner region, an edge, an edge region which is arranged between theinner region and the edge, a first semiconductor zone of a firstconduction type in the inner region and edge region and at least onesecond semiconductor zone of a second conduction type that iscomplementary to the first conduction type, said second semiconductorzone being arranged in the inner region in the region of the front,producing a connection electrode in the second semiconductor zone on thefront of the semiconductor body, and irradiating the front withhigh-energy particles using the connection electrode as a mask in orderto produce recombination centers in the semiconductor body for thepurpose of recombining charge carriers of the first and secondconduction types.

The operation of introducing the high-energy particles can be followedby a temperature process for stabilizing the recombination centers inthe semiconductor body. The temperature process can be carried out at atemperature of between 220° C. and 360° C. for a period of between 30minutes and 4 hours. The high-energy particles can be protons or heliumatoms. The energy of the high-energy particles and the thickness of theconnection electrode that can be used as a mask are matched to oneanother in such a manner that recombination centers are produced, atleast approximately, exclusively in the second semiconductor zonebeneath the connection electrode. The edge region of the semiconductorbody may have at least one third semiconductor zone of the secondconduction type in the region of the front, the energy of thehigh-energy particles being selected in such a manner that therecombination centers in the edge region are produced, at leastapproximately, exclusively in the first semiconductor zone. Thesemiconductor body may have a third semiconductor zone whose dopingconcentration, starting from the inner zone, decreases in the directionof the edge. The third semiconductor zone may adjoin the secondsemiconductor zone. The semiconductor body may have at least two thirdsemiconductor zones which are arranged at a distance from one another inthe direction of the edge and at a distance from the secondsemiconductor zone. A fourth zone of the first conduction type can beproduced in the region of the back of the semiconductor body, saidfourth zone being more highly doped than the first zone.

The object can also be achieved by a semiconductor component comprisinga semiconductor body which has a front, a back, an inner region, an edgeregion which is arranged between the inner region and an edge, a firstsemiconductor zone of a first conduction type in the inner region andedge region and at least one second semiconductor zone of a secondconduction type that is complementary to the first conduction type, saidsecond semiconductor zone being arranged in the inner region in theregion of the front, a connection electrode which is applied to thefront of the semiconductor body in the second semiconductor zone, and arecombination zone which has recombination centers and is arrangedbeneath the connection electrode in the second semiconductor zone and inthe edge region in the first semiconductor zone.

At least one third semiconductor zone of the second conduction type canbe provided in the edge region in the region of the front. There can bea third semiconductor zone whose doping concentration, starting from theinner zone, decreases in the direction of the edge. The thirdsemiconductor zone may adjoin the second semiconductor zone. There canbe at least two fourth semiconductor zones which are arranged at adistance from one another in the direction of the edge and at a distancefrom the second semiconductor zone. There can be a fourth zone of thefirst conduction type in the region of the back of the semiconductorbody, said fourth zone being more highly doped than the first zone.

The inventive method for producing a semiconductor component involvesproviding a semiconductor body which has a front, a back, an innerregion, an edge, an edge region which is arranged between the innerregion and the edge, a first semiconductor zone of a first conductiontype in the inner region and edge region and at least one secondsemiconductor zone of a second conduction type that is complementary tothe first conduction type, said second semiconductor zone being arrangedin the inner region in the region of the front. The production of such asemiconductor body having a pn junction in the inner region and havingan edge region is sufficiently well known, with the result that it willnot be discussed in any more detail.

A connection electrode which can be used to make electrical contact withthe second semiconductor zone of the subsequent component is thenproduced in the second semiconductor zone on the front of thesemiconductor body. The front of the semiconductor body is thenirradiated with high-energy particles, for example protons or heliumatoms, with the connection electrode being used as a mask for theirradiation process and ensuring that, in that region of the inner zonewhich is covered by the connection electrode, the particles do notpenetrate as deeply into the semiconductor body as in that region of theedge zone which is not covered by the connection electrode.

The particles which are introduced into the semiconductor body producerecombination centers, with irradiation preferably being followed by atemperature step which is used to stabilize the recombination centers.The recombination centers used are double blanks or A centers(blanks/oxygen complexes) which are produced by irradiation and thetemperature step which optionally follows. The heat treatment is carriedout, for example, at temperatures of between 220° C. and 360° C. for aperiod of between 30 minutes and 4 hours, depending on the temperature.

The defects which are caused by irradiation and are used asrecombination centers have higher recombination effectiveness in ann-doped region than in a p-doped region and thus shorten the chargecarrier lifetime to a greater extent in an n-doped region. Theirradiation energy of the high-energy particles and the thickness of theconnection electrode that is used as a mask are matched to one anotherin such a manner that recombination centers are produced, at leastapproximately, exclusively in the second semiconductor zone beneath theconnection electrode.

This makes it possible, when the first semiconductor zone is n-doped andthe second semiconductor zone is p-doped, to shorten the charge carrierlifetime to a lesser degree in the second semiconductor zone in theinner region (which is desirable in order to set the static and dynamicproperties), while the charge carrier lifetime is considerablyshortened, as desired, in the first semiconductor zone in the edgeregion in order to diminish the avalanche effects (explained) during theswitching-off operation.

In order to increase the dielectric strength in the edge region, theedge region of the semiconductor body has at least one thirdsemiconductor zone of the second conduction type in the region of thefront. In this case, one exemplary embodiment has at least two thirdsemiconductor zones which are at a distance from one another in thedirection of the edge and are at a distance from the secondsemiconductor zone. The mode of action of such third semiconductor zoneswhich preferably surround the inner region in an annular manner and aretherefore referred to as field rings is described, for example, inBaliga: “Power Semiconductor Devices”, PWS Publishing, 1995, pages98-100.

In another exemplary embodiment, a third semiconductor zone adjoins thesecond semiconductor zone, the doping of this third semiconductor zonedecreasing in the direction of the edge. A semiconductor zone of thistype is also referred to as a VLD (Variation of Lateral Doping) zone.

The irradiation energy of the high-energy particles is selected in sucha manner that the particles in the edge region penetrate so deeply intothe semiconductor body that the recombination zones are essentiallyproduced beneath the third semiconductor zone which is used to increasethe dielectric strength in the edge region, that is to say in the firstsemiconductor zone. The semiconductor body is advantageously beveled atthe edge, this constituting a further known measure for increasing thedielectric strength in the edge region but not being required for theeffectiveness of the method.

Using the connection electrode as a mask, the inventive method makes itpossible, in a simple manner, to produce a recombination zone havinglower recombination effectiveness in the second semiconductor zone inthe inner region and a recombination zone having higher recombinationeffectiveness in the first semiconductor zone in the edge region.

The inventive semiconductor component comprises a semiconductor bodywhich a front, a back, an inner region, an edge, an edge region which isarranged between the inner region and the edge, a first semiconductorzone of a first conduction type in the inner region and edge region andat least one second semiconductor zone of a second conduction type thatis complementary to the first conduction type, said second semiconductorzone being arranged in the inner region in the region of the front. Aconnection electrode is applied to the front of the semiconductor bodyin the second semiconductor zone. In addition, there is a recombinationzone which has recombination centers and is arranged beneath theconnection electrode in the second semiconductor zone and in the edgeregion in the first semiconductor zone.

In order to increase the dielectric strength in the edge region, fieldrings of the second conduction type or a VLD zone is/are preferablyprovided in the edge region beneath the front.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be explained in more detail below inexemplary embodiments and with reference to figures, in which:

FIG. 1 shows a partial cross section through a semiconductor body onwhich the inventive method is based,

FIG. 2 shows the semiconductor body as shown in FIG. 1 during the nextmethod steps for producing a semiconductor component,

FIG. 3 shows a partial cross section through a semiconductor componentwhich has been produced using the inventive method,

FIG. 4 shows a schematic plan view of the semiconductor component shownin FIG. 3,

FIG. 5 shows a partial cross section through another semiconductor bodywhich forms the starting point for an exemplary embodiment of theinventive method,

FIG. 6 shows the semiconductor body as shown in FIG. 5 during furthermethod steps for producing the semiconductor component, and

FIG. 7 shows a partial cross section through an inventive semiconductorcomponent.

Unless stated otherwise, identical reference symbols denote identicalparts with the same meaning in the figures.

DETAILED DESCRIPTION

The inventive method for producing a semiconductor component isexplained below with reference to FIGS. 1 to 3 for producing a verticalpower diode. The method involves providing a semiconductor body 100which is partially shown in cross section in FIG. 1. The semiconductorbody 100 has a front 101, a back 102 and an edge 105 which runs in abeveled manner in the exemplary embodiment. The semiconductor bodycomprises an inner region 103 at a distance from the edge 105 and anedge region 104 arranged between the inner region 103 and the. edge. Thesemiconductor body 100 shown has n-type basic doping, the semiconductorregions having this basic doping being referred to below as the firstsemiconductor zone 20. A p-doped second semiconductor zone 30 isintroduced into said first semiconductor zone 20 in the inner region 103beneath the front 101, with the result that a pn junction is formedbetween said second semiconductor zone 30 and the first semiconductorzone 20 in the inner region 103. Provided in the edge region 104 beneaththe front 101 are p-doped field rings 62, 64 which, starting from thesecond semiconductor zone 30, are arranged at a distance from oneanother in the direction of the edge 105 and at a distance from thesecond semiconductor zone 30. In the region of the front 101, an n-dopedsemiconductor zone 70, which is used as a channel stopper, directlyadjoins the edge 105.

The semiconductor body 100 also comprises a highly n-doped fifthsemiconductor zone 50 which adjoins the first semiconductor zone 20 inthe region of the back 102. This highly n-doped semiconductor zone 50which is used as an n-type emitter forms the cathode zone of thesubsequent semiconductor component in the form of a diode. In the innerregion 103, the first semiconductor zone 20 forms the n-type base andthe p-doped second semiconductor zone 30, which is used as a p-typeemitter, forms the anode zone. The field rings 62, 64 in the edge region104 are used, in a known manner, to increase the dielectric strength ofthe component in the edge region. The bevel (which is likewise known) ofthe edge 105 serves the same purpose.

The provision of a semiconductor body (shown in FIG. 1) having thesemiconductor zones which have been explained is sufficiently wellknown, with the result that it is possible to omit a further explanationof this.

As shown in FIG. 2, a connection electrode 40 is applied to the front101 of the semiconductor body 100 in the region of the secondsemiconductor zone 30 (p-type emitter), said connection electrode beingused to make subsequent electrical contact with the p-type emitter 30.The front 101 of the semiconductor body is then irradiated withhigh-energy particles, for example protons or helium atoms, whichpenetrate into the semiconductor body 100. In this case, the penetrationdepth beneath the connection electrode 40 is shallower than in the otherregions, since the connection electrode 40 brakes the high-energyparticles even before they penetrate into the semiconductor body 100.Irradiating the semiconductor body 100 with high-energy particles servesto produce recombination centers in the semiconductor body with the aimof shortening the charge carrier lifetime. These recombination centers,for example double blanks or A centers, are formed by defects in thecrystal lattice, which defects are caused by the high-energy particles.During irradiation, for example with protons or helium atoms, use ismade, in this case, of the effect that the highest concentration ofdefects is produced in a relatively narrow zone, the “end of range”region, in which the irradiation particles emit most of their energy andare thus braked. This irradiation with high-energy particles ispreferably followed by a heat treatment method in which thesemiconductor body is heated to temperatures of between 220° C. and 360°C. for a period of between 30 minutes and 4 hours in order to stabilizethe recombination centers.

The penetration depth of the high-energy particles depends on theirradiation energy and, in the region of the connection electrode 40, onthe thickness of this connection electrode 40. In this case, theirradiation energy and the thickness of this connection electrode 40 arematched to one another in such a manner that the recombination centersare produced beneath the connection electrode 40 in the p-doped secondsemiconductor zone 30. The recombination centers have lowerrecombination effectiveness in the p-doped zone 30 than in the n-dopedfirst semiconductor zone 20 in the edge region, with the result that therecombination centers in this p-doped region 30 shorten the chargecarrier lifetime to a lesser degree than in the n-doped regions 10. Inaddition to in the first semiconductor zone 20 in the edge region 104,it is also desirable to shorten the charge carrier lifetime to a certaindegree in the p-doped anode zone 30 in order to be able to use it to setthe static and dynamic properties of the component.

The irradiation energy of the high-energy particles is also selected insuch a manner that the recombination centers in the edge region 104 areessentially produced in the first semiconductor zone 20 (n-type base)beneath the field rings 62, 64 and the channel stopper 70.

As the result, FIG. 3 schematically shows the physical position of therecombination centers beneath the connection electrode 40 in the innerregion 103 and in the edge region 104, the reference symbol 80A denotingthe recombination zone in the anode zone 30 and the reference symbol 80Bdenoting the recombination zone in the edge region 104. In this case,the recombination zone 80A beneath the connection electrode is closer tothe front 101, since the high-energy particles are braked in this regionby the connection electrode 40 even before they penetrate into thesemiconductor body 100. In the edge region 104, which does not contain aconnection electrode, the high-energy particles correspondinglypenetrate more deeply into the semiconductor body 101, with the resultthat the recombination zone 80B is further away from the front 101 here.Since the irradiation energy of the individual particles is subject tofluctuations and on account of random scatter effects in thesemiconductor lattice, recombination zones 80A, 80B having a particularwidth in the vertical direction of the semiconductor body are produced,this width being dependent, inter alia, on the irradiation energy. Inthis case, most of the recombination centers are in the “end of range”region of irradiation.

The inventive method makes it possible, in a simple manner, to produce avertical semiconductor component having a pn junction, in the edgeregion 104 of which the charge carrier lifetime is effectively shortenedby means of recombination centers, with the charge carrier lifetimelikewise additionally being shortened in the inner region 103 in thesecond semiconductor zone 30 (which, in the case of diodes, is used as ap-type emitter) but to a lesser degree than in the edge region.

The inventive method is not restricted to producing semiconductor diodesbut rather can be used for any desired vertical semiconductorcomponents, for example MOS transistors, IGBTs or thyristors, which havea pn junction in the inner region and in which it is desirable toshorten the charge carrier lifetime in the edge region.

In addition to the abovementioned possible way of using the thickness ofthe connection electrode 40 to set the penetration depth of thehigh-energy particles in the inner region 103, it is also possible toinfluence this penetration depth using the choice of electrode material.In this case, the high-energy particles penetrate less deeply into thesemiconductor body 100, the “denser” the electrode material. Examples ofsuitable electrode materials are: gold (Au), copper (Cu), molybdenum(Mb), titanium (Ti) or tungsten (W).

FIG. 4 schematically shows a plan view of the front 101 of thesemiconductor component which is shown in FIG. 3 and, in the example, isformed in a circular manner with a circumferential edge 105 and edgeregion 104. It will be pointed out that the illustration in FIG. 4, inwhich the area of the edge region 104 is considerably larger than thatof the inner region 103, is not to scale.

FIGS. 5 to 7 illustrate a method for producing a further semiconductorcomponent in the form of a diode, the method differing from that shownin FIGS. 1 to 3 by virtue of the fact that, instead of field rings(reference symbols 62, 64 in FIGS. 1 to 3), the semiconductor body usedhas a VLD zone 60 as a third semiconductor zone, which adjoins thesecond semiconductor zone 30 in the direction of the edge 105 and thedoping of which, starting from the second semiconductor zone 30,decreases in the direction of the edge 105. A VLD zone of this type isachieved, for example, by the zone 60 being constructed from a pluralityof semiconductor zones 60A, 60B, 60C which are arranged next to oneanother in the lateral direction. The doping within these semiconductorzones 60A-60C may be respectively homogeneous in this case, the dopingdecreasing from semiconductor zone 60A, 60B to semiconductor zone 60B,60C in the direction of the edge 105.

The other method steps for producing the semiconductor component, namelyapplying a connection electrode 40, irradiating the front 101 of thesemiconductor body with high-energy particles and, optionally, a heattreatment step that follows irradiation, correspond to the methodexplained with reference to FIGS. 1 to 3. In this case, the energy ofthe high-energy particles is also selected here in such a manner thatthe recombination zone 80B in the edge region 104 is essentiallyproduced in the n-type base 20, that is to say beneath the VLD zone 60.

In order to complete the components, a further connection electrode 90may be applied to the back 102, said further connection electrode makingit possible to make electrical contact with the highly n-dopedsemiconductor zone and being used as a cathode electrode in the case ofdiodes.

List of reference symbols  20 First semiconductor zone, n-type base  30Second semiconductor zone, p-type emitter  50 Fourth semiconductor zone,n-type emitter  60, 60A, 60B, 60C VLD zone  62, 64 Third semiconductorzone, field rings  70 Channel stopper  80A, 80B Recombination zone 100Semiconductor body 101 Front 102 Back 103 Inner region 104 Edge region105 Edge

1. A method for producing a semiconductor component, said methodcomprising the following method steps of: providing a semiconductor bodywhich has a front side, a back side, an inner region, an edge, an edgeregion which is arranged between the inner region and the edge, a firstsemiconductor zone of a first conduction type in the inner region andedge region and at least one second semiconductor zone of a secondconduction type that is complementary to the first conduction type, saidsecond semiconductor zone being arranged in the inner region in theregion of the front, producing a connection electrode in the secondsemiconductor zone on the front of the semiconductor body, irradiatingthe front with high-energy particles using the connection electrode as amask in order to produce recombination centers in the semiconductor bodyfor the purpose of recombining charge carriers of the first and secondconduction types, wherein the recombination centers form a recombinationzone in the semiconductor body, the recombination zone being arrangedbeneath the connection electrode in the second semiconductor zone closerto the front and in the edge region in the first semiconductor zonefarther away from the front such that the recombination zone extendsdeeper into the semiconductor body from the front in the firstsemiconductor zone than in the second semiconductor zone.
 2. A method asclaimed in claim 1, wherein the operation of introducing the high-energyparticles is followed by a temperature process for stabilizing therecombination centers in the semiconductor body.
 3. A method as claimedin claim 1, wherein the temperature process is carried out at atemperature of between 220° C. and 360° C. for a period of between 30minutes and 4 hours.
 4. A method as claimed in claim 1, wherein thehigh-energy particles are protons or helium atoms.
 5. A method asclaimed in claim 1, wherein the energy of the high-energy particles andthe thickness of the connection electrode that is used as a mask arematched to one another in such a manner that recombination centers areproduced, at least approximately, exclusively in the secondsemiconductor zone beneath the connection electrode.
 6. A method asclaimed in claim 1, wherein the edge region of the semiconductor bodyhas at least one third semiconductor zone of the second conduction typein the region of the front, the energy of the high-energy particlesbeing selected in such a manner that the recombination centers in theedge region are produced, at least approximately, exclusively in thefirst semiconductor zone.
 7. A method as claimed in claim 6, wherein thesemiconductor body has a third semiconductor zone whose dopingconcentration, starting from the inner zone, decreases in the directionof the edge.
 8. A method as claimed in claim 7, wherein the thirdsemiconductor zone adjoins the second semiconductor zone.
 9. A method asclaimed in claim 6, wherein the semiconductor body has at least twothird semiconductor zones which are arranged at a distance from oneanother in the direction of the edge and at a distance from the secondsemiconductor zone.
 10. A method as claimed in claim 1, wherein a fourthzone of the first conduction type is produced in the region of the backof the semiconductor body, said fourth zone being more highly doped thanthe first zone.
 11. A method as claimed in claim 1, wherein therecombination zone extends along a substantial length of the secondsemiconductor zone and along a partial length of the first semiconductorzone.
 12. A method as claimed in claim 1, wherein the recombinationcenters arranged in the first semiconductor zone have a higherrecombination effectiveness than the recombination centers arranged inthe second semiconductor zone.